A lithium ion battery is now widely used as a battery for a personal computer and cell phone.
When a battery is charged, the battery voltage is usually checked, and charging is stopped to prevent overcharging when the voltage increases to higher than a threshold level.
A lithium ion battery is increased in impedance after years of use. When a lithium battery with increased impedance is charged, the battery voltage is increased by the charging voltage and voltage generated by the impedance, an overcharge protection circuit functions, and charging may not be started. Other batteries whose impedance increases as the number of times of charging increases may not be charged.